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Subject[RFC 17/47] mtd: nand: stm_nand_bch: automatically set EEC mode if requested
Date
Here we automatically select the strongest ECC scheme compatible with
the size of the OOB.

Signed-off-by: Lee Jones <lee.jones@linaro.org>
---
drivers/mtd/nand/stm_nand_bch.c | 40 ++++++++++++++++++++++++++++++++++++++++
1 file changed, 40 insertions(+)

diff --git a/drivers/mtd/nand/stm_nand_bch.c b/drivers/mtd/nand/stm_nand_bch.c
index f5a3e80..60a7800 100644
--- a/drivers/mtd/nand/stm_nand_bch.c
+++ b/drivers/mtd/nand/stm_nand_bch.c
@@ -32,6 +32,13 @@
/* NANDi BCH Controller properties */
#define NANDI_BCH_SECTOR_SIZE 1024

+/* BCH ECC sizes */
+static int bch_ecc_sizes[] = {
+ [BCH_18BIT_ECC] = 32,
+ [BCH_30BIT_ECC] = 54,
+ [BCH_NO_ECC] = 0,
+};
+
/* Bad Block Table (BBT) */
struct nandi_bbt_info {
uint32_t bbt_size; /* Size of bad-block table */
@@ -135,6 +142,25 @@ static void nandi_disable_interrupts(struct nandi_controller *nandi,
writel(val, nandi->base + NANDBCH_INT_EN);
}

+/* Select strongest ECC scheme compatible with OOB size */
+static int bch_set_ecc_auto(struct nandi_controller *nandi,
+ struct mtd_info *mtd)
+{
+ int oob_bytes_per_sector = mtd->oobsize / nandi->sectors_per_page;
+ int try_ecc_modes[] = { BCH_30BIT_ECC, BCH_18BIT_ECC, -1 };
+ int m, ecc_mode;
+
+ for (m = 0; try_ecc_modes[m] >= 0; m++) {
+ ecc_mode = try_ecc_modes[m];
+ if (oob_bytes_per_sector >= bch_ecc_sizes[ecc_mode]) {
+ nandi->bch_ecc_mode = ecc_mode;
+ return 0;
+ }
+ }
+
+ return -EINVAL;
+}
+
static void nandi_set_mtd_defaults(struct nandi_controller *nandi,
struct mtd_info *mtd, struct nand_chip *chip)
{
@@ -792,6 +818,20 @@ static int stm_nand_bch_probe(struct platform_device *pdev)
0x10000) ? true : false;
mtd->writebufsize = mtd->writesize;

+ /* Set ECC mode */
+ if (pdata->bch_ecc_cfg == BCH_ECC_AUTO) {
+ err = bch_set_ecc_auto(nandi, mtd);
+ if (err) {
+ dev_err(nandi->dev, "insufficient OOB for BCH ECC\n");
+ return err;
+ }
+ } else {
+ nandi->bch_ecc_mode = pdata->bch_ecc_cfg;
+ }
+
+ info->ecclayout.eccbytes =
+ nandi->sectors_per_page * bch_ecc_sizes[nandi->bch_ecc_mode];
+
return 0;
}

--
1.8.3.2


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